I am not familiar with an ELFA HIV
test and thus cannot directly compare it to the stand
ELISA assay. If the
test is liscensed for use by the US FDA or the EU, it is reliable. If it is not or you do not know and are concerned, then you should get re-tested with a test you are assured is reliable. The odds of infection from a single exposure to a partner of unknown HIV status however is very low. Thus, even without testing, your risk for HIV from a single exposure is very, very low.